In the packaging industry, ozone (O3) is commonly used for sterilization of drinking water. During the bottling process, ozone is applied as the last step to disinfect and kill any air-borne microorganisms that may be present at the time of filling. Due to its strong oxidizing character, ozone can effectively kill microorganisms, however, ozone can also cause undesirable reactions with the plastic package. The products and byproducts of these reactions are responsible for the off-taste odor that characterizes ozonated water, especially if packaged in flexible polyolefin containers.
The effects of ozone on polyethylene-based polymers and other polymers have been published. For example, see the following: (a) Migration of Volatile Degradation Products into Ozonated Water from Plastic Packaging Materials; Song, Y. S.; Al-Taher, F.; Sadler, G. Food Additives & Contaminants, (2003), 20(10), 985-994 (identifies volatile compounds and their concentration in water after ozonation of several types of plastic materials, and compares the concentration found, with that approved by the FDA); (b) The Influence of Different Sterilization Methods on Chemical and Physical Properties of Food Packaging Made of Plastics; Steiner, I.; Grundschober, J.; Dobias, J.; Sipek, M.; Washuttl, J.; Voldrich, M.; Lebensmittelchemie, (1999), 53(3), 59, Abstract (discusses the effects of sterilization (ozone, H2O2, ClO2 and γ-irradn) on polyethylene bottles, foils and PET); (c) Changes in a Polyethylene Food Packaging Film Following Ozone Sterilization; Steiner, Ingrid; Deutsche Lebensmittel-Rundschau, (1991), 87(4), 107-12, Abstract (discusses the effects of ozone sterilization on polyethylene film and on the antioxidant butylhydroxyanisole); (d) Ozonation Effect on Taste in Water Packaged in High Density Polyethylene Bottles; White, C. H.; Gough, R. H.; McGregor, J. U.; Vickroy, V. V.; Journal of Dairy Science, (1991), 74(1), 96-9, Abstract (discusses the off-taste produced by the ozonation of water, bottled in containers formed from high density polyethylene, and also discusses a treatment using butylated hydroxytoluene); (e) Surface Ozonation and Photooxidation of Polyethylene Film; Peeling, James; Clark, David T; Journal of Polymer Science, Polymer Chemistry Edition (1983), 21(7), 2047-55 (describes the surface effects of ozone and photo-oxidation on film formed from high density polyethylene and low density polyethylene); and (f) Ozone and Its Current and Future Application in the Food Industry; Kim Jin-Gab; Yousef Ahmed E; Khadre Mohammed A; Advances in Food and Nutrition Research (2003), 45 167-218, Abstract (reviews the use of ozone as a sanitizer in the food industry).
Zeolites, silicates and flavor protectants have been used in an attempt to eliminate odors from sterilized water. U.S. Publication No. 2002/0020672 discloses an in-situ method of treating ozone sterilized water to remove unwanted odors and tastes produced during the sterilization process. Odors are removed by the incorporation of a zeolite into the cap or cap liner of a container.
However, the use of one or more additives to improve taste and odor, such as a zeolite, a silicate or a flavor protectant, will increase the cost of a resin formulation.
International Publication No. WO 92/13029 discloses a process for eliminating odor producing and taste producing substances in plastic materials, by adding a substantially hydrophobic aluminum silicate molecular sieve to the plastic material. The plastic material is preferably an ethylene plastic or a propylene plastic.
European Patent EP 0687706B1 (Abstract) discloses a polyolefin-based composition comprising a lubricating agent, and a zeolite (crystalline aluminosilicate). The polyolefin composition can be used for molded articles, such as plastic bottles.
International Publication No. WO 96/04833 discloses a liner composition for a potable fluid container. The composition contains an inactivated hydrazine, and/or an inorganic sulfite and/or a tocopherol compound for preventing off-flavors due to the presence of aldehydes in the fluid.
German application DE 100 60 478 A1 (Abstract) discloses a method for obtaining water free from bacteria and smells, comprising treating of water with ozone in a container filled with active carbon and/or substances containing zeolite.
International Publication No. WO 00/68106 discloses a bottled liquid, such as bottled water, where the liquid has little or no plastic off-taste. The bottle contains a closure liner which comprises a plastic matrix and an organic slip agent dispersed in the plastic matrix. The slip agent is substantially fully ethylenically saturated, and the liner is substantially free of an ethylenically unsaturated compound. Suitable ethylenically saturated slip agents include behenamide, polysiloxane, fluoropolymers, paraffin wax, carbowax, synthetic mineral oil and mixtures thereof.
U.S. Publication No. 2004/0222165 discloses methods of packaging ozone sterilized products in plastic film containers, wherein adverse organoleptic reactions or interactions are substantially reduced. Ozone sterilized water is packaged in flexible plastic pouches having an inner polyethylene liner formed from polyethylene, which does not contain slip agents or other organic processing aids that may react with ozone.
International Publication No. WO2004/067273 discloses a multilayer film that contains a first and second outer layer, each including a polymer; and an internal layer including an oxygen scavenger. At least one of the first and second outer layers includes a blend of a polymer, a siloxane having a viscosity of from 1×107 centistokes to 5×107 centistokes, and an antiblock agent.
However, there is a need for polyolefin compositions for use in packaging of ozone treated liquids, and especially ozone treated water, which lead to a reduction in the off-taste and odor of the liquid. There a further need for polyolefin compositions that does not require the use of additives, in addition to the standard processing additives, for taste and odor reduction. Also, there is a need in the packaging industry for polyolefins with improved heat seal strength and/or hot tack strength, which can be used to improve package integrity and/or increase packaging speed, with minimal formation of by-products that cause off-taste and odor. These needs and others have been met by the following invention.